A. Field of the Invention
The device of the present invention generally relates to circuit breakers and, more particularly, to electrical contacts for molded case circuit breakers.
B. Description of the Prior Art
Circuit breakers and, more particularly, molded case circuit breakers are old and well known in the prior art. Examples of such devices are disclosed in U.S. Pat. Nos. 2,186,251; 2,492,009; 3,239,638; 3,525,959; 3,590,325; 3,614,685; 3,775,713; 3,783,423; 3,805,199; 3,815,059; 3,863,042; 3,959,695; 4,077,025; 4,166,205; 4,258,403; and 4,295,025. In general, prior art molded case circuit breakers have been provided with movable contact arrangements and operating mechanisms designed to provide protection for an electrical circuit or system against electrical faults, specifically, electrical overload conditions, low level short circuit or fault current conditions, and, in some cases, high level short circuit or fault current conditions. Prior art devices have utilized an operating mechanism having a trip mechanism for controlling the movement of an over-center toggle mechanism to separate a pair of electrical contacts upon an overload condition or upon a short circuit or fault current condition. At least some prior art devices use contacts that "blow-open", i.e., separate prior to the sequencing of the operating mechanism through a trip operation, to rapidly interrupt the flow of high level short circuit or fault currents.
While many prior art devices have provided adequate protection against fault conditions in electrical circuits, a need exists for dimensionally small molded case circuit breakers capable of fast, effective and reliable operation and, more specifically, for compact, movable, upper electrical contacts capable of rapid movement away from associated lower electrical contacts during high level short circuit or fault current conditions, such movement being independent of and in advance of the sequencing of the operating mechanisms through a trip operation.